<HTML>
<HEAD>
  <TITLE> DwNntpClient Man Page </TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<H2>
  <FONT COLOR="navy"> NAME </FONT>
</H2>
<P>
DwNntpClient -- Class for handling the client side of an NNTP session
<H2>
  <FONT COLOR="navy"> SYNOPSIS </FONT>
</H2>
<PRE>class DW_EXPORT DwNntpClient : public <A HREF="protocol.html">DwProtocolClient</A> {

public:

    enum {
        kCmdNoCommand=0,
        kCmdArticle,
        kCmdBody,
        kCmdHead,
        kCmdStat,
        kCmdGroup,
        kCmdHelp,
        kCmdIhave,
        kCmdLast,
        kCmdList,
        kCmdNewgroups,
        kCmdNewnews,
        kCmdNext,
        kCmdPost,
        kCmdQuit,
        kCmdSlave
    };
    <A HREF="nntp.html#DwNntpClient">DwNntpClient</A>();
    virtual ~DwNntpClient();
    virtual int <A HREF="nntp.html#Open">Open</A>(const char* aServer, DwUint16 aPort=119);
    DwObserver* <A HREF="nntp.html#SetObserver">SetObserver</A>(DwObserver* aObserver);
    int <A HREF="nntp.html#ReplyCode">ReplyCode</A>() const;
    const DwString&amp; <A HREF="nntp.html#StatusResponse">StatusResponse</A>() const;
    const DwString&amp; <A HREF="nntp.html#TextResponse">TextResponse</A>() const;
    int <A HREF="nntp.html#Article">Article</A>(int aNumber=(-1));
    int <A HREF="nntp.html#Article">Article</A>(const char* aMsgid);
    int <A HREF="nntp.html#Body">Body</A>(int aNumber=(-1));
    int <A HREF="nntp.html#Body">Body</A>(const char* aMsgid);
    int <A HREF="nntp.html#Head">Head</A>(int aNumber=(-1));
    int <A HREF="nntp.html#Head">Head</A>(const char* aMsgid);
    int <A HREF="nntp.html#Stat">Stat</A>(int aNumber=(-1));
    int <A HREF="nntp.html#Stat">Stat</A>(const char* aMsgid);
    int <A HREF="nntp.html#Group">Group</A>(const char* aNewsgroupName);
    int <A HREF="nntp.html#Help">Help</A>();
    int <A HREF="nntp.html#Ihave">Ihave</A>(const char* aMsgId);
    int <A HREF="nntp.html#Last">Last</A>();
    int <A HREF="nntp.html#List">List</A>();
    int <A HREF="nntp.html#Newgroups">Newgroups</A>(const char* aDate, const char* aTime,
        DwBool aIsGmt=DwFalse, const char* aDistributions=0);
    int <A HREF="nntp.html#Newnews">Newnews</A>(const char* aNewsgroups, const char* aDate,
        const char* aTime, DwBool aIsGmt=DwFalse, const char* aDistribution=0);
    int <A HREF="nntp.html#Next">Next</A>();
    int <A HREF="nntp.html#Post">Post</A>();
    int <A HREF="nntp.html#Quit">Quit</A>();
    int <A HREF="nntp.html#Slave">Slave</A>();
    int <A HREF="nntp.html#SendData">SendData</A>(const DwString&amp; aStr);
    int <A HREF="nntp.html#SendData">SendData</A>(const char* aBuf, int aBufLen);
};
</PRE>
<H2>
  <FONT COLOR="navy"> DESCRIPTION </FONT>
</H2>
<P>
<B><TT>DwNntpClient</TT></B> is a class that handles the client side of an
NNTP session. Specifically, <B><TT>DwNntpClient</TT></B> provides facilities
for opening a connection to an NNTP server, sending commands and data to
the server, receiving responses and data from the server, and closing the
connection. The protocol implemented is the Network News Transport Protocol,
as specified in RFC-977.
<P>
<B><TT>DwNntpClient</TT></B> is derived from
<B><TT><A HREF="protocol.html">DwProtocolClient</A></TT></B>. For information
about inherited member functions, especially member functions for detecting
failures or errors, see the man page for
<B><TT>DwProtocolClient</TT></B>.
<P>
In an NNTP session, the client sends commands to the server and receives
responses from the server. A client command consists of a command word and
zero or more argument words. A server response consists of a status line
and possibly some additional lines of text. The status line consists of a
three-digit numeric reply code followed by additional information. The reply
code indicates a success or failure condition. In some cases, the server
sends lines of text immediately after the status line.
<B><TT>DwNntpClient</TT></B> provides facilities for you to send commands
to the server and receive responses from the server.
<P>
<B><TT>DwNntpClient</TT></B> has only a default constructor. On Win32 platforms,
it is possible for the constructor to fail. (It calls WSAStartup().) You
should verify that the constructor succeeded by calling the inherited member
function <B><TT>DwProtocolClient::LastError()</TT></B> and checking for a
zero return value.
<P>
To open a connection to the server, call the member function
<B><TT>Open()</TT></B> with the name of the server as an argument.
<B><TT>Open()</TT></B> accepts an optional argument that specifies the TCP
port that the server listens to. The default port is the standard NNTP port
(119). <B><TT>Open()</TT></B> may fail, so you should check the return value
to verify that it succeeded. To close the connection, call the inherited
member function <B><TT>DwProtocolClient::Close()</TT></B>. To check if a
connection is open, call the inherited member function
<B><TT>DwProtocolClient::IsOpen()</TT></B>. <B><TT>IsOpen()</TT></B> returns
a boolean value that indicates whether or not a call to
<B><TT>Open()</TT></B> was successful; it will not detect failure in the
network or a close operation by the remote host.
<P>
For each NNTP command, <B><TT>DwNntpClient</TT></B> has a member function
that sends that command and receives the server's response. If the command
takes any arguments, then those arguments are passed as function arguments
to the command function. The command functions return the numeric value of
the three-digit reply code returned by the server. Your program must check
the reply code to determine whether or not the command was accepted and performed
by the server. In some cases, because of a communications error or some other
error, it is not possible for the command function to send the command or
receive the response. When this happens, the command function will return
0. You can determine the precise error or failure by calling the inherited
member functions <B><TT>DwProtocolClient::LastError()</TT></B> or
<B><TT>DwProtocolClient::LastFailure()</TT></B>.
<P>
After each command is sent, <B><TT>DwNntpClient</TT></B> receives the server's
response and remembers it. The member function
<B><TT>ReplyCode()</TT></B> returns the numeric value of the reply code received
in response to the last command. <B><TT>StatusResponse()</TT></B> returns
the entire status response from the server, including the reply code. If
no status response is received, possibly because of a communications error
or failure, <B><TT>ReplyCode()</TT></B> returns zero and
<B><TT>StatusResponse()</TT></B> returns an empty string.
<P>
The server sends a status response, including a reply code, for all all NNTP
commands. For some commands, such as when the client requests an article
body, the server sends a multi-line text response immediately following the
status response. Multi-line text responses can be received in either of two
ways. The simplest way is to call the member function
<B><TT>TextResponse()</TT></B> after a command completes successfully. This
simple method works fine for non-interactive applications. It can be a problem
in interactive applications, however, because there is no data to display
to a user until the entire text response is retrieved. An alternative method
allows your program to retrieve the text response one line at a time as it
is received. To use this method, you must define a subclass of
<B><TT>DwObserver</TT></B> and assign an object of that class to the
<B><TT>DwNntpClient</TT></B> object using the member function
<B><TT>SetObserver()</TT></B>. <B><TT>DwObserver</TT></B> is an abstract
class, declared in protocol.h, that has just one pure virtual member function
<B><TT>Notify()</TT></B>. After each line of the text response is received,
<B><TT>DwNntpClient</TT></B> will call the <B><TT>Notify()</TT></B> member
function of its assigned <B><TT>DwObserver</TT></B> object. Each invocation
of <B><TT>Notify()</TT></B> should call the <B><TT>DwNntpClient</TT></B>
member function <B><TT>TextResponse()</TT></B> to retrieve the next line
of the text response. Note that you cannot use both of these methods at the
same time: if an observer is assigned, <B><TT>TextResponse()</TT></B> returns
only the last line received, not the entire multi-line text response.
<P>
Certain NNTP commands, such as the POST command, require the NNTP client
to send multiple lines of text to the server. To perform this bulk data transfer,
<B><TT>DwNntpClient</TT></B> provides the member function
<B><TT>SendData()</TT></B>. In the current implementation,
<B><TT>SendData()</TT></B> does not convert end of line characters, so it
is your responsibility to convert the end of line characters to CR LF, if
necessary. (You may use the utility function
<B><TT>DwToCrLfEol()</TT></B> to do the conversion.)
<B><TT>SendData()</TT></B> will perform the character stuffing to protect
'.' at the beginning of a line, and it will append the final [CR LF] '.'
CR LF. It is possible to divide data and make multiple calls to
<B><TT>SendData()</TT></B>; however, if you do so, please note the following
paragraph.
<P>
Note: Because of a feature (some might say bug) in the current implementation,
<B><TT>SendData()</TT></B> will not detect a '.' at the beginning of a line
if the CR LF '.' sequence is split between two calls to
<B><TT>SendData()</TT></B>. This problem will probably be resolved in a future
version, but be aware that such a change will require a change in
<B><TT>DwNntpClient</TT></B>'s interface.
<H2>
  <FONT COLOR="navy"> Public Member Functions </FONT>
</H2>
<P>
<FONT COLOR="teal"><B> <A NAME="DwNntpClient">DwNntpClient</A>() </B></FONT>
<P>
Initializes the <B><TT>DwNntpClient</TT></B> object. It is possible for the
constructor to fail. To verify that the constructor succeeded, call the member
function <B><TT>LastError()</TT></B> and check that it returns zero. (In
the Win32 implementation, the constructor calls the Winsock function
<B><TT>WSAStartup()</TT></B>, which may fail.)
<P>
<FONT COLOR="teal"><B> virtual int <A NAME="Open">Open</A>(const char* aServer,
DwUint16 aPort=119) </B></FONT>
<P>
Opens a TCP connection to the server <B><TT>aServer</TT></B> at port
<B><TT>aPort</TT></B>. <B><TT>aServer</TT></B> may be either a host name,
such as "news.acme.com" or an IP number in dotted decimal format, such as
"147.81.64.60". The default value for <B><TT>aPort</TT></B> is 119, the
well-known port for NNTP assigned by the Internet Assigned Numbers Authority
(IANA).
<P>
If the connection attempt succeeds, the server sends a response.
<B><TT>Open()</TT></B> returns the server's numeric reply code. The full
response from the server can be retrieved by calling
<B><TT>StatusResponse()</TT></B>.
<P>
If the connection attempt fails, <B><TT>Open()</TT></B> returns 0. To determine
what error occurred when a connection attempt fails, call the inherited member
function <B><TT>DwProtocolClient::LastError()</TT></B>. To determine if a
failure also occurred, call the inherited member function
<B><TT>DwProtocolClient::LastFailure()</TT></B>.
<P>
<FONT COLOR="teal"><B> DwObserver*
<A NAME="SetObserver">SetObserver</A>(DwObserver* aObserver) </B></FONT>
<P>
Sets the observer object that interacts with the
<B><TT>DwNntpClient</TT></B> object to retrieve a multi-line text response.
If an observer is set, <B><TT>DwNntpClient</TT></B> will call the observer's
<B><TT>Notify()</TT></B> method after each line of the text response is received.
To remove an observer, call <B><TT>SetObserver()</TT></B> with a NULL argument.
<B><TT>SetObserver()</TT></B> returns the previously set observer, or NULL
if no observer was previously set.
<P>
<FONT COLOR="teal"><B> int <A NAME="ReplyCode">ReplyCode</A>() const
</B></FONT>
<P>
Returns the numeric value of the three-digit reply code received from the
server in response to the last client command. If no response was received,
<B><TT>ReplyCode()</TT></B> returns zero.
<P>
<FONT COLOR="teal"><B> const DwString&amp;
<A NAME="StatusResponse">StatusResponse</A>() const </B></FONT>
<P>
Returns the entire status response last received from the server. If no response
was received, perhaps because of a communications failure,
<B><TT>StatusResponse()</TT></B> returns an empty string.
<P>
<FONT COLOR="teal"><B> const DwString&amp;
<A NAME="TextResponse">TextResponse</A>() const </B></FONT>
<P>
If no observer is set for this object, <B><TT>TextResponse()</TT></B> returns
a string that comprises the entire sequence of lines received from the server.
Otherwise, if an observer <B><TT>is</TT></B> set for this object,
<B><TT>TextResponse()</TT></B> returns only the most recent line received.
<P>
<FONT COLOR="teal"><B> int <A NAME="Article">Article</A>(int aNumber=(-1))
<BR>
int Article(const char* aMsgid) </B></FONT>
<P>
Sends the NNTP ARTICLE command and returns the reply code received from the
server. If no response is received, the function returns zero. The optional
argument <B><TT>aNumber</TT></B> specifies the number of an article to retrieve.
If <B><TT>Article()</TT></B> is called with the default argument, the ARTICLE
command is sent to the server with no argument. <B><TT>aMsgId</TT></B> specifies
the message id of an article to retrieve.
<P>
<FONT COLOR="teal"><B> int <A NAME="Body">Body</A>(int aNumber=(-1)) <BR>
int Body(const char* aMsgid) </B></FONT>
<P>
Sends the NNTP BODY command and returns the reply code received from the
server. If no response is received, the function returns zero. The optional
argument <B><TT>aNumber</TT></B> specifies the number of an article whose
body should be retrieved. If <B><TT>Body()</TT></B> is called with the default
argument, the BODY command is sent to the server with no argument.
<B><TT>aMsgId</TT></B> specifies the message id of the article to access.
<P>
<FONT COLOR="teal"><B> int <A NAME="Head">Head</A>(int aNumber=(-1)) <BR>
int Head(const char* aMsgid) </B></FONT>
<P>
Sends the NNTP HEAD command and returns the reply code received from the
server. If no response is received, the function returns zero. The optional
argument <B><TT>aNumber</TT></B> specifies the number of an article whose
header lines should be retrieved. If <B><TT>Head()</TT></B> is called with
the default argument, the HEAD command is sent to the server with no argument.
<B><TT>aMsgId</TT></B> specifies the message id of the article to access.
<P>
<FONT COLOR="teal"><B> int <A NAME="Stat">Stat</A>(int aNumber=(-1)) <BR>
int Stat(const char* aMsgid) </B></FONT>
<P>
Sends the NNTP STAT command and returns the reply code received from the
server. If no response is received, the function returns zero. The optional
argument <B><TT>aNumber</TT></B> specifies the number of an article to access.
If <B><TT>Stat()</TT></B> is called with the default argument, the STAT command
is sent to the server with no argument. <B><TT>aMsgId</TT></B> specifies
the message id of the article to access.
<P>
<FONT COLOR="teal"><B> int <A NAME="Group">Group</A>(const char* aNewsgroupName)
</B></FONT>
<P>
Sends the NNTP GROUP command and returns the reply code received from the
server. The argument <B><TT>aNewsgroupName</TT></B> specifies the newgroup
to be selected. If no response is received, the function returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Help">Help</A>() </B></FONT>
<P>
Sends the NNTP HELP command and returns the reply code received from the
server. If no response is received, the function returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Ihave">Ihave</A>(const char* aMsgId)
</B></FONT>
<P>
Sends the NNTP IHAVE command and returns the reply code received from the
server. <B><TT>aMsgId</TT></B> specifies the message id of the article to
be sent. If no response is received, the function returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Last">Last</A>() </B></FONT>
<P>
Sends the NNTP LAST command and returns the reply code received from the
server. If no response is received, the function returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="List">List</A>() </B></FONT>
<P>
Sends the NNTP LIST command and returns the reply code received from the
server. If no response is received, the function returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Newgroups">Newgroups</A>(const char*
aDate, const char* aTime, DwBool aIsGmt=DwFalse, const char* aDistributions=0)
</B></FONT>
<P>
Sends the NNTP NEWGROUPS command and returns the reply code received from
the server. If no response is received, the function returns zero.
<B><TT>aDate</TT></B> is the date in the form YYMMDD, where YY is the two
digit year, MM is the month, and DD is the day of the month.
<B><TT>aTime</TT></B> is the time in the form HHMMSS, where HH is hours,
MM is minutes, and SS is seconds. If <B><TT>aIsGmt</TT></B> is true, the
optional GMT argument will be sent. <B><TT>aDistributions</TT></B> specifies
the optional list of distribution groups.
<P>
<FONT COLOR="teal"><B> int <A NAME="Newnews">Newnews</A>(const char* aNewsgroups,
const char* aDate, const char* aTime, DwBool aIsGmt=DwFalse, const char*
aDistribution=0) </B></FONT>
<P>
Sends the NNTP NEWNEWS command and returns the reply code received from the
server. If no response is received, the function returns zero.
<B><TT>aNewsgroups</TT></B> is the newsgroups argument for the command.
<B><TT>aDate</TT></B> is the date in the form YYMMDD, where YY is the two
digit year, MM is the month, and DD is the day of the month.
<B><TT>aTime</TT></B> is the time in the form HHMMSS, where HH is hours,
MM is minutes, and SS is seconds. If <B><TT>aIsGmt</TT></B> is true, the
optional GMT argument will be sent. <B><TT>aDistributions</TT></B> specifies
the optional list of distribution groups.
<P>
<FONT COLOR="teal"><B> int <A NAME="Next">Next</A>() </B></FONT>
<P>
Sends the NNTP NEXT command and returns the reply code received from the
server. If no response is received, perhaps because of an error, the function
returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Post">Post</A>() </B></FONT>
<P>
Sends the NNTP POST command and returns the reply code received from the
server. If no response is received, perhaps because of an error, the function
returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Quit">Quit</A>() </B></FONT>
<P>
Sends the NNTP QUIT command and returns the reply code received from the
server. If no response is received, perhaps because of an error, the function
returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="Slave">Slave</A>() </B></FONT>
<P>
Sends the NNTP SLAVE command and returns the reply code received from the
server. If no response is received, perhaps because of an error, the function
returns zero.
<P>
<FONT COLOR="teal"><B> int <A NAME="SendData">SendData</A>(const DwString&amp;
aStr) <BR>
int SendData(const char* aBuf, int aBufLen) </B></FONT>
<P>
Sends bulk data to the server and returns the reply code received. A bulk
data transfer follows a POST or IHAVE command and is used to send a complete
article to the server.
<P>
In the current implementation, <B><TT>SendData()</TT></B> does not convert
end of line characters, so it is your responsibility to convert the end of
line characters to CR LF, if necessary. (You may use the utility function
<B><TT>DwToCrLfEol()</TT></B> to do the conversion.)
<B><TT>SendData()</TT></B> will perform the character stuffing to protect
'.' at the beginning of a line, and it will append the final [CR LF] '.'
CR LF. It is possible to divide the data and make multiple calls to
<B><TT>SendData()</TT></B>; however, this may cause problems in the current
implementation if a CR LF '.' sequence is split between calls.
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